1. Field of the Invention
The present invention generally relates to a socket connector comprising conductive terminals for electrically connecting an electronic device, such as a central processing unit (CPU) module, to a circuit board, and more particular to the structure of the terminals.
2. The Related Arts
Socket connectors for mounting an electronic device, such as a central processing unit (CPU) module, to a circuit board are well known and are commonly used in the computer industry. FIG. 1 of the attached drawings shows an example of the socket connectors that is referred to as ZIF (Zero Insertion Force) socket connector. The socket connector, generally designated with reference numeral 10, comprises a housing 12, made of an insulation material, defining an array of open cells 14 in which conductive terminals (not shown in FIG. 1) are received and a cover 16 movably supported on the housing 12. The cover 16 defines through holes 18 corresponding to the cells 14 of the housing 12. The cover 16 carries a CPU module 20 with pin legs 22 of the CPU module 20 extending through the holes 18 of the cover 16 and partially projecting into the cells 14. An actuator 24 drives the cover 16 to move in a predetermined direction A in such a manner to bring the pin legs 24 of the CPU module 20 into contact with the terminals of the housing 12 thereby forming electrical connection therebetween. Examples of socket connectors of this type are also disclosed in U.S. Pat. Nos. 4,498,725, 5,833,483, 6,059,596, 6,142,810, and 6,159,032.
A number of different terminals for the socket connectors are available. They can be roughly classified as single-beam terminals and dual-beam terminals. Terminals of both types have a base section received and securely retained in the cell of the housing and a tail extending from the base and beyond a lower face of the housing for being soldered to the circuit board. A signal-beam terminal has a single beam extending from base section substantially in a direction opposite to the tail and forming a spring arm on a free end of the beam, while a dual-beam terminal has two beams opposite to each other. An example of the dual beam-terminal is illustrated in U.S. Pat. No. 4,498,725 and shown is FIG. 2 of the attached drawings. The dual-beam terminal, generally designated with reference numeral 30 in FIG. 2, comprises a base section 32 and a tail 34 extending from the base section 32 in a downward direction (as viewed in FIG. 2). Two beams 36 extend from the base section 32 in an upward direction that is substantially opposite to the downward direction of the tail 34. The beams 36 are opposite to each other and spring arms 38 are formed on free ends thereof and extending in a horizontal direction substantially parallel to the predetermined direction A and normal to the upward and downward directions. Free ends 40 of the spring arms 38 are convergent to each other for reducing the space therebetween.
Since the beams 36 and the spring arms 38 are made substantially opposite to each other, forming a mirror symmetry configuration. The pin leg 22 of the CPU module 20 that engages with the spring arms 38 of the terminal 30 is first inserted into the space between the spring arms 38. When the cover 16 moves in the direction A, the pin leg 22 is driven into the reduced space between the free ends 40 of the spring arms 38 for forming electrical connection therebetween.
The terminal 30 is usually made by stamping a metal plate , followed by mechanically forming the beams 36 and the spring arms 38. Conventionally, a major surface of each beam 36 is made substantially parallel to an imaginary plane defined by the direction A and the upward direction whereby the pin leg 22 is guided in the direction A. Such a conventional design suffers certain deficiencies. For example, the gap size between the free ends 40 of the spring arms 38 is difficult to adjust. Spring rate of the spring arms 38 is also difficult to adjust and this in turn makes the normal force acting upon the pin leg 22 by the spring arms 38 difficult to adjust in order to achieve optimum electrical and mechanical engagement between the spring arms 38 and the pin leg 22. Such deficiencies are even more severe in a housing having compactly arranged terminals for the terminal pitch is reduced. Reduced terminal pitch indicates the spring arms 38 must be shortened, leading to difficulty for adjustment of the above parameters.
Thus, it is desired to have a terminal configured to overcome the above mentioned deficiencies.
An object of the present invention is to provide a dual-beam terminal of a socket connector that allows easy adjustment of contact gap between opposite spring arms thereof.
Another object of the present invention is to provide a dual-beam terminal of a socket connector that allows easy adjustment of spring rate and thus the normal force acting upon a pin leg engaging therewith.
A further object of the present invention is to provide a dual-beam terminal having a performance adjustable configuration of the beams.
To achieve the above objects, in accordance with the present invention, a socket connector comprises a housing positioned on a circuit board and movably supporting a cover. Cells are defined in the housing for receiving and retaining dual-beam terminals. The cover carries a central processing unit module having pin legs extending through holes defined in the cover and partially projecting into the cells of the housing. The cover is movable in a moving direction to bring the pin legs into engagement with the corresponding terminals. Each dual-beam terminal comprises a base section received and firmly retained in the corresponding cell and a tail extending from the base section and beyond the housing for being soldered to the circuit board.. Two beams extend from the base section, substantially opposite to the tail. Each beam forms a spring arm on a free end thereof. The spring arms are opposite to and spaced from each other for engaging the corresponding pin leg therebetween. The beams are symmetric with respect to an imaginary plane that is normal to the base section and coincident with the moving direction. Each beam has a major surface angularly offset from the imaginary plane and thus forming a first included angle with the imaginary plane. The major surface also forms a second included angle with the base section. The included angles are smaller than 90 degrees and greater than 0 degree. Preferably, the included angles are 45 degrees. The angularly offset configuration of the beams allows easy adjustment of the space between the spring arms and thus adjustment of the performance parameters of the terminals.